1. The Field of the Invention
The present invention relates generally to the storage of molecular hydrogen. More particularly, the present invention relates to the storage of hydrogen using carbon nanospheres.
2. The Related Technology
The limited supplies of fossil fuels and the increasing number of densely populated metropolitan cities with poor local air quality have spurred interest in developing new energy sources. Hydrogen has emerged as a promising candidate for replacing various aspects of the world's current energy production system. Hydrogen is attractive as a fuel source because it can be produced from renewable sources and burns pollution-free or can be used in pollution-free fuel cells, as the combustion or reaction product is water.
The single greatest impediment to the use of hydrogen as an energy source is the lack of a convenient, cost-effective storage system for vehicles. Traditional methods for storing hydrogen employ large, heavy high-pressure tanks that are not practical or cost effective for widespread use in the transportation industry.
Extensive research is being performed to develop a hydrogen storage system suitable for the transportation industry and other industries that require a light-weight and safe storage mechanism. Possible current approaches include (i) physical storage via compression or liquefaction, (ii) chemical storage in irreversible hydrogen carriers (e.g. methanol or ammonia), (iii) reversible metal and chemical hydrides, and (iv) gas-on-solid adsorption.
Carbon based adsorbents have been studied for their potential to store hydrogen. Initial efforts to store hydrogen in carbon involved “activated” carbons. However, activated carbons are ineffective in storing hydrogen because only a small fraction of the pores in the typically wide pore-size distribution are small enough to interact strongly with hydrogen molecules at room temperature and moderate pressures. Recently, single-walled and multi-walled nanotubes have been studied for their potential to store hydrogen. Recent work relating to carbon nanotubes has shown that various differences in carbon nanotubes can have significant impact on the ability of carbon nanotubes to store hydrogen. However, despite extensive efforts to optimize carbon nanotubes for hydrogen storage, storage capacity in carbon nanotubes is not currently feasible for most applications.